Final answer:
The melting point of soap produced through saponification of a triglyceride is lower than that of the triglyceride itself, due to changes in molecular structure and intermolecular forces.
Step-by-step explanation:
The melting point of soap made from a triglyceride formed from one molecule of glycerol and three molecules of stearic acid is expected to be lower than that of the actual triglyceride. This is attributed to the chemical process known as saponification, where triglycerides are hydrolyzed in the presence of a base to produce soap, which consists of the sodium salts of fatty acids.
During the saponification process, the ester bonds in the triglycerides are broken, and the fatty acids are released to form sodium salts. These salts have different physical properties than the original triglycerides. Because the triglyceride molecule, such as tristearin, is highly ordered due to the similar fatty acid chains, which allows for tight packing and stronger intermolecular forces, it has a higher melting point. In contrast, the resulting soap molecules tend to have less ordered structures with weaker intermolecular forces due to their ionic nature and thus a lower melting point.